ADR 0038: Reference Peripheral Handlers Are Permissively Licensed

• Status: accepted
• Date: 2026-10-13
• Supersedes: — (an exception to ADR-0011 for one directory)

Context

fjarr.ota applies peripheral components (MCU firmware, motor controllers, a GNSS receiver, a router) through handlers: separate programs speaking a small JSON contract (docs/32). Fjarr ships three reference handlers in M8 (u-blox configuration, a CAN flasher, router configuration). Customers will adapt them into handlers for their own devices, and those often encode a supplier’s proprietary update procedure. Under ADR-0011 the reference handlers would be AGPL-3.0, so an adapted handler a customer distributes would be AGPL too, which is a reason for a robot company not to use them at all.

Options considered

1. AGPL like the rest of the open core. Consistent, but works against the handlers’ purpose: to be copied and changed.
2. MIT for the reference handlers and the contract’s examples. Customers fork them freely; the value Fjarr protects (the agent, the updater, the fleet side) stays AGPL or commercial.
3. No reference handlers, only the contract. Avoids the question, but leaves every customer to start from nothing.

Decision

Option 2 (Erik, 2026-10-13). The reference handlers and the handler contract’s example code are MIT-licensed, in a directory of their own with its own LICENSE file. The handler contract itself is specified in docs/32 like the rest of the protocol. Everything else under ADR-0011 is unchanged: fjarr-update, its appliers, the agent and the fleet side stay AGPL-3.0 or commercial.

Consequences

• Customers can turn a reference handler into a proprietary one without obligations; competitors could reuse them too, which costs little, since they are simple glue around tools the customer installs.
• Contributions to the reference handlers are accepted under MIT; the CLA (ADR-0011) still covers them.
• The licence boundary is a directory: code moved from it into the AGPL tree becomes AGPL, never the other way.